code: def test_copy_wait_cpu_cpu():
      prev_stream = CPUStream
      next_stream = CPUStream
      _test_copy_wait(prev_stream, next_stream)
  
file_path: fairscale/tests/nn/pipe/test_copy.py
imports: import pytest
  import torch
  from fairscale.nn.pipe.copy import Copy, Wait
  from fairscale.nn.pipe.stream import CPUStream, current_stream, get_device, is_cuda, new_stream, use_stream
label_desc: Use image node_id 2 for calling a global function with example usage: test_copy_wait_cpu_cpu() without return types